For years following its discovery,
Azibius was difficult to classify. Originally described by Jean Sudre in 1975 as a possible 'paromomyiform' (a type of
plesiadapiform),
A. trerki was also interpreted as a
hyopsodontid by paleoanthropologist
Frederick S. Szalay that same year. The following year, paleoanthropologist
Philip D. Gingerich reclassified it as an
adapid. Throughout the 1990s and 2000s, debates over its classification continued, with some researchers suggesting it might be related to macroscelidids (
elephant shrews), while others supported initial interpretations as adapids or plesiadapiforms (particularly
carpolestids). In 2006, paleoanthropologist
Marc Godinot favored a relationship between
Azibius and simians, but tentatively suggested
Azibius may be more closely related to
toothcombed primates, which include all extant strepsirrhines. This latter view has gained increasing support with the reclassification of
Algeripithecus (once considered a
basal simian) as a closely related azibiid. The
mandible of
Algeripithecus indicates it had an inclined
canine tooth, similar to that found in toothcombed primates. Although the anterior dentition of azibiids is unknown, they may have possessed a toothcomb, indicating an ancient
stem lineage of
lemuriform primates in Africa, possibly descended from an early Asian branch of adapiforms such as a primitive branch of
cercamoniines predating
Donrussellia (one of the oldest European adapiforms).
Tabelia hammadae, which was also considered to be one of the oldest known simians along with
Algeripithecus, was shown to be a
synonym of
Azibius when more complete fossils were discovered at Gour Lazib between 2003 and 2009. Likewise, the second upper molar (M2) of
Dralestes hammadaensis have been reinterpreted as being the upper fourth premolar (P4) of
Azibius and has been considered a synonym. However, in 2010, Godinot cautiously suggested that
Dralestes may be a synonym of
Algeripithecus based on a blade-like premolar. He also reasserted his view that
Algeripithecus was a simian based on its upper molar morphology and hypothesized that this applied to all azibiids, favoring his earlier view that they may be early simians instead of stem lemuriforms. In 2011, Marivaux
et al. published an interpretation of recently discovered
talus bones found at Gour Lazib, which they claimed were more similar to those of living strepsirrhines and extinct adapiforms, not simians, thus reinforcing the strepsirrhine status favored by Tabuce
et al. two years earlier. The tali morphology also differed radically from those of plesiadapiforms, confirming that azibiids are true primates. Remains of a second, unnamed species of
Azibius, cf.
Azibius sp., have been discovered in the HGL-50 layer at Gour Lazib. It is known for a few upper and lower teeth. These teeth are three times larger than those of
A. trerki. A larger right talus has also been found, and is assumed to belong to this new species. ==Anatomy and physiology==